The present invention relates to apparatus for underground mining operations, where the hazards of roof collapse command that precautionary measures and procedures be instituted to protect personnel and equipment. Primary needs are those connected with stabilization of the active face area especially the roof in either conventional or continuous mining, and in developmental openings, including breakthroughs, either for room and pillar, panel or longwall mining. Existing regulations and practices in conjunction with roof control require that no person proceed beyond the last permanent support without temporary supports.
In normal practice, timbering or roof bolting takes place in accordance with an approved plan, wherein it is a requirement that the point supports, timber and/or bolts, be installed stepwise along lines parallel with the face.
A new developmental technique of roof support uses liquid polymer impregnation of the roof rock to stabilize that surface. After the polymer sets, the roof surface is stabilized continuously over the entire surface in contrast to the point of contact support afforded by timber or bolts. Because of the rock structure and orientation of fissures and crevices within the roof, it is necessary for effective roof control to inject the fluid polymer by plan in a regular pattern stepwise along the length and width of the mine tunnel. As an example, a spacing of two feet between polymer injection points along the length and breadth of a tunnel is contemplated in conjunction with an injection apparatus which advances stepwise by a distance of two feet every five minutes.
Because the hazard of roof collapse exists, even as measures are taken to permanently support the roof, it is necessary to provide temporary roof support during those procedures. Also, in the polymer method, hydraulic pressures from fluid injection increase the hazard of rock fall or roof collapse, especially when cure time for competency of the polymer is, for example, 25 minutes. Thus, with such a polymer, temporary support at each injection point is required for a 25 minute period equivalent to five steps of 2feet distance lengthwise by the machine through the tunnel. Therefore, for tasks such as progressive polymer injection and progressive timbering and bolting, it is desirable to have a temporary roof support mechanism capable of advancing stepwise in a straight line through the mine tunnel at a step-rate suited to the task at hand. Also, a canopy over the mechanism is needed to protect personnel and equipment from rock fall and roof collapse which may occur prior to effective permanent stabilization.
Prior techniques of temporary mine roof support and operator protective devices mounted on mining machines are shown in U.S. Pat. Nos. 2,711,634 and 3,768,574. Continuous and advancing roof support arrangements are also disclosed in prior patents, e.g., U.S. Pat. Nos. 3,377,105; 2,904,319; and 3,240,022. A walking device is disclosed in U.S. Pat. No. 3,524,321. Disadvantages of the prior mechanisms are found in load bearing, wherein the mechanism chassis is designed to carry the roof support load, or in the use of sliding or rolling techniques of progressively advancing the roof spport members. Sliding and rolling, frequently while the members are under roof stresses, are made difficult by abrasion, the high surface pressure and unevenness of the tunnel surfaces. High maintenance is generally required in the mines to keep slide and rolling mechanisms properly functional.
What is needed in the mines is a device for advancing through a tunnel while providing: protection for the person-operator from roof falls, incremental advancement in a straight line, continuous temporary support for the roof while permanent support is implemented, transmission of roof load directly into the floor without stressing the primary machine structure, and movement of supports in an unstressed condition. Equipment requiring relatively little maintenance is also needed.